In the first hour that the same-sex ruling was legal in the State of California, couples who where just married filed out of San Francisco's City Hall on June 16, 2008.6/16/08Photo by Frederic Larson / The Chronicle

Photo: Frederic Larson, The Chronicle

In the first hour that the same-sex ruling was legal in the State...

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A limousine drives by protestors and supporters outside City Hall, Monday June 16, 2008, in San Francisco, Calif. Lacy Atkins /The San Francisco Chronicle

Photo: Lacy Atkins, The Chronicle

A limousine drives by protestors and supporters outside City Hall,...

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A truck, bearing signs against same-sex marriage, circles San Francisco City Hall shortly before the first marriage on Monday, June 16, 2008.Photo by Noah Berger / Special to the Chronicle

Californians will get to vote in November on a state constitutional amendment to ban same-sex marriage, the state Supreme Court decided Wednesday.

In a unanimous order, without comment, the court dismissed a lawsuit by gay rights advocates seeking to remove an initiative sponsored by conservative religious groups from the Nov. 4 ballot. The measure, Proposition 8, would overturn the court's 4-3 ruling May 15 that allowed gay and lesbian couples to marry in California.

The suit, on behalf of couples who had challenged the state's previous ban on same-sex marriage, argued that Prop. 8 would destroy fundamental rights that cannot be changed by a voter initiative. The court rarely takes up legal challenges to a ballot measure before an election, and could consider the same issue in another lawsuit if the measure passes.

The suit was "a desperate effort to keep the amendment away from the democratic process," said attorney Glen Lavy of the Alliance Defense Fund, which represents sponsors of Prop. 8.

Like one of the laws the court struck down in May, Prop. 8 declares that "only a marriage between a man and a woman is valid or recognized in California."

The court majority declared two months ago that denying marriage to same-sex couples discriminates against them because of their sexual orientation and violates their fundamental right - contained in the right of privacy that state voters approved in 1972 - to marry the partner of their choice.

The lawsuit against Prop. 8 argued that the one-sentence initiative was actually a broad attack on basic rights recognized by the court - a measure that would simultaneously deprive one group of fundamental freedoms by majority vote and strip the courts of their ability to enforce constitutional guarantees.

Although its backers call it a constitutional amendment, Prop. 8 is actually a constitutional revision, the suit contended. A revision must be submitted to the voters by a two-thirds majority of the state Legislature.

The last time the court accepted such an argument was in 1990, when it overturned part of a voter-approved constitutional amendment on crime. In that case, the justices said a provision requiring state judges to follow federal interpretations of defendants' rights was a broad attack on judicial authority and a "fundamental change in our ... governmental plan."

Lawyers for the Prop. 8 backers argued that an amendment to restore the state's previous definition of marriage would leave courts with "full authority to continue protecting the rights of minorities." They said equally far-reaching changes in California law - for example, the restoration of the death penalty in 1972 and the overhaul of the tax system under Proposition 13 in 1978 - were accomplished by initiative.